Spur Gears - Norfolk Bearings and Supply Company, Inc.
Spur Gears - Norfolk Bearings and Supply Company, Inc.
Spur Gears - Norfolk Bearings and Supply Company, Inc.
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D<br />
Worms & Worm <strong>Gears</strong><br />
Selection Procedure<br />
Approximate input horsepower <strong>and</strong> output torque ratings for<br />
Boston stock worm <strong>and</strong> worm gear combinations from 12 to<br />
3 DP are listed on Pages 97, 98. These ratings are for<br />
hardened, ground <strong>and</strong> polished worms operating with bronze<br />
worm gears. For other combinations multiply the listed ratings<br />
by the following percentages:<br />
Hardened, ground <strong>and</strong> polished steel worms with cast iron<br />
gears 50%. Unhardened steel worms with cast iron gears<br />
25%.<br />
These ratings are listed at selected worm speeds. Ratings for<br />
inter mediate speeds can be interpolated from the values<br />
indicated.<br />
These ratings are based on gears operating with a Service<br />
Factor of 1.0, properly mounted in accordance with good<br />
design practice <strong>and</strong> continuously lubricated with a sufficient<br />
supply of oil.<br />
Service<br />
Factor<br />
Boston worms <strong>and</strong> worm gears provide an effective answer for such power<br />
transmission applications as high-ratio speed reduction, limited space, right-angle<br />
shafts <strong>and</strong> non-intersecting shafts. When properly applied, they are the smoothest<br />
<strong>and</strong> quietest form of gearing. Steel worms <strong>and</strong> cast iron or bronze worm gears are<br />
available in single, double or quadruple threads, 48 to 3 diametral pitch.<br />
Acetal worms <strong>and</strong> worm gears are available in single thread, 48 to 24<br />
diametral pitch.<br />
1. Determine service factor.<br />
a. Using Application Classification Chart I, pages 323, 324,<br />
determine service factor or<br />
b. With knowledge of operating conditions <strong>and</strong> load<br />
classification, select service factor from Table 1.<br />
2. Determine Design Horsepower.<br />
Design HP = Application Load x Service Factor (Table 1)<br />
3. Select worm gear set with horsepower capacity equal to [or<br />
greater than] design horsepower determined in Step 2.<br />
Operating Conditions<br />
0.8 Uniform—not more than 15 minutes in 2 hours.<br />
1.0<br />
1.25<br />
1.50<br />
TABLE 1<br />
Moderate Shock—not more than 15 minutes in 2 hours.<br />
Uniform—not more than 10 hours per day.<br />
Moderate Shock—not more than 10 hours per day.<br />
Uniform—more than 10 hours per day.<br />
Heavy Shock—not more than 15 minutes in 2 hours.<br />
Moderate Shock—more than 10 hours per day.<br />
1.75 Heavy Shock—not more than 10 hours per day.<br />
2.0 Heavy Shock—more than 10 hours per day.<br />
Heavy shock loads <strong>and</strong>/or severe wear conditions may require the use of higher<br />
service factors. Consultation with factory is recommended in these<br />
applications.<br />
96 Boston Gear 800-825-6544 P-1930-BG 04/10
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